1. Field of the Invention
The present invention is in the field of cathodic protection of metallic water tanks and more particularly in the field of suspension devices for suspending anodes and reference cells within said water tanks from the roof or other suitable structure which is located in the tank vertically above or at the top of the water in the tank. Specifically, the present invention relates to an apparatus for suspending the anodes and reference cells within the tank, in the water, providing resilient adjustment of the electrical lines and/or structural lines from which the anodes and reference cells are suspended so that the ice which forms in the tank does not adversely affect the anodes or reference cells by creating excessive downward forces thereon. The apparatus is most specifically designed to fit any standard water tank and may be installed in any said standard water tank. The apparatus is specifically adapted to be placed in any of a plurality of configurations within the water tank, depending on how large the water tank is and how many anodes are required therein for proper cathodic protection of the tank.
2. Description of the Prior Art
Water tanks used for municipal water supplies, industrial purposes and the like are subject to constant corrosion due to corrosive action from water contained in the tank, since such water tanks generally are constructed of steel. If such corrosion is not prevented, the tank will eventually wear away or be so weakened that the tank may structurally fail. This may result in the release of large amounts of water from extreme heights, with consequent danger to lives and property. Accordingly, it is desirable to protect such water tanks from the adverse effects of corrosion.
Water tanks are commonly protected both by various coatings which are applied to the inside of the water tank, such as epoxies and the like which prevent or reduce corrosive action and also are protected by various cathodic protection systems which produce a regulated, electrolytic effect to counteract the corrosive electrolysis which takes place at the water tank wall.
Cathodic protection apparatus is well developed and is in wide use at the present time. Such apparatus normally consists of one or more arrays of anodes placed in the water within the tank, apparatus to maintain the anodes positioned within the tank, electrical connecting apparatus connecting the anodes to a source of electrical current, a control mechanism for maintaining a constant voltage in the water in the tank and one or more reference cells with which to measure the voltage level within the water in the tank. A typical electrical system used to monitor the electrical voltage in the water within the water tank and to adjust the current input to the anode in response to the measured electrical voltage as the electrical conductivity of the water varies due to varying temperature, mineral content and the like, is shown in the U.S. Pat. No. issued to Maurin 3,516,917. Another typical electrical system for controlling the current input to the cathodic protection system in the water tank is shown in U.S. Pat. No. 3,425,921 issued to Sudrabin.
In the past in tanks which have experienced icing and have been equipped with cathodic protection devices, the anodes and other apparatus of the cathodic protection devices have typically been mounted in the bottom of the water tank, as shown in the cathodic protection device in the patent issued to Jacobs, U.S. Pat. No. 3,718,554. One disadvantage inherent in the cathodic protection devices which have been mounted on the bottom of the water tank is that such devices tend to become fouled with ice as the water in the tank, with the ice at its surface, drops below the level of the cathodic protection device. Then, while ice is still on the water and the water level in the tank rises, the ice may break or damage the cathodic protection device as the ice level rises past the level of the cathodic protector. Ice may also form along the sides and at the bottom of the tank. Ice at the tank bottom may entrap a tank-bottom-mounted electrolysis device while ice formed at the sides of the tank may encapsulate an anode suspended from the top of the tank where the anode has been disposed too closely to the side of the tank. Also, with the devices mounted on the bottom of the tanks, the current distribution within the water tends to be non-uniform and inefficient due to the confinement of the apparatus to a relatively narrow stratum of water at the bottom of the tank.
Spring suspended anodes hanging from the tops of the water tanks have long been known with one approach to a cathodic protection device suspended from the roof of the water tank being that shown in the U.S. Pat. No. issued to Palmer 3,855,102. The Palmer approach has definite disadvantages, one of which being that the apparatus shown therein, and others similar to it waste a certain volume of space at the top of the water tank because the water level cannot be permitted to rise to the level of the suspension means since ice might foul the spring suspension devices from which the anodes are suspended or might lock onto the electrical leads. If these devices are fouled and cannot function properly and if there is a large volume of ice, the weight of the ice pulling down on the suspension devices and the electrical lead wires as the water level in the tank drops may break the suspension devices and lead wires or may even break the top structure of the tank, to which the suspension devices are attached. Accordingly, it is required when the Palmer device or a similar spring suspension apparatus is used that a disproportionately large upper volume of the tank remain dormant, i.e., not be filled with water, so that the spring suspension devices do not become fouled with ice.